Image forming apparatus

ABSTRACT

An image forming apparatus including an optical scanning device that scans an object to be scanned with a beam in a main scanning direction includes a first rotation fulcrum unit and a second rotation fulcrum unit that are respectively provided in the optical scanning device on one side and on the other side in an orthogonal direction orthogonal to the main scanning direction. The first rotation fulcrum unit is provided outside a scanning area of the beam in the main scanning direction. The optical scanning device is provided rotatably around a virtual rotation axial line connecting the first rotation fulcrum unit and the second rotation fulcrum unit.

BACKGROUND 1. Field

The present disclosure relates to an image forming apparatus such as acopier, a multifunction peripheral, a printer, and a facsimile, andparticularly to an image forming apparatus including an optical scanningdevice that scans an object to be scanned with a beam in a main scanningdirection.

2. Description of the Related Art

As an image forming apparatus including an optical scanning device thatscans an object to be scanned with a beam in a main scanning direction,there are an apparatus described in Japanese Unexamined PatentApplication Publication No. 2002-258198 and an apparatuses described inJapanese Unexamined Patent Application Publication No. 2010-66402, forexample.

That is, Japanese Unexamined Patent Application Publication No.2002-256198 discloses a configuration in which rocking fulcrums of ahousing of an optical scanning device are provided at two points on astraight line (virtual rotation axial line) that crosses obliquely withrespect to a shaft core of an object to be scanned (scanning area) andan adjustment point is provided at one point on another straight lineorthogonal to the straight line so that an attitude of the housing ofthe optical scanning device with respect to the object to be scanned ina torsion direction is adjusted at the adjustment point.

Japanese Unexamined Patent Application Publication No. 2010-66402discloses a configuration in which one positioning axis is provided on a(scanning area) center part in an irradiation direction of a rotarypolygon mirror in an optical scanning device, and when a vertex of atriangle is set on the positioning axis, two installation holes areprovided at the other two points (on a virtual rotation axial line) ofthe triangle and positions for installing the two installation holes areset to be adjustable with the one positioning axis as a center.

However, in the configuration described in Japanese Unexamined PatentApplication Publication No. 2002-258198 and the configuration describedin Japanese Unexamined Patent Application Publication No. 2010-66402,the virtual rotation axial line of the optical scanning device passesthrough the center part of the scanning area in the main scanningdirection. Then, a beam scanning trajectory that is a scanningtrajectory of a beam output from the optical scanning device is inclinedto both sides with respect to the main scanning direction with one pointof the center part in the scanning area as a center. Thus, the beamscanning trajectory needs to be adjusted so as to be along the mainscanning direction while three points of the one point of the centerpart in the scanning area in the main scanning direction and two pointsin both end parts are being confirmed. Accordingly, an adjustmentoperation for adjusting the beam scanning trajectory so as to be alongthe main scanning direction becomes complicated.

Then, the disclosure provides an image forming apparatus which includesan optical scanning device that scans an object to be, scanned with abeam in a main scanning direction and which is able to realizesimplification of an adjustment operation for adjusting a scanningtrajectory of the beam, which is output from the optical scanningdevice, so as to be along the main scanning direction.

SUMMARY

It is desirable to provide an image forming apparatus including anoptical scanning device that scans an object to be scanned with a beamin a main scanning direction, and the image forming apparatus includes afirst rotation fulcrum unit and a second rotation fulcrum unit that arerespectively provided in the optical scanning device on one side and onthe other side in an orthogonal direction orthogonal to the mainscanning direction, in which the first rotation fulcrum unit is providedoutside a scanning area of the beam in the main scanning direction, andthe optical scanning device is provided rotatably around a virtualrotation axial line connecting the first rotation fulcrum unit and thesecond rotation fulcrum unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of an image forming apparatusaccording to an embodiment of the disclosure, as seen from a frontsurface;

FIG. 2 is a schematic perspective view of an image forming apparatusbody illustrated in FIG. 1, as seen obliquely left downward;

FIG. 3 is a perspective view of an optical scanning device and an objectto be scanned, as seen obliquely downward from a front surface side;

FIG. 4 is a perspective view illustrating a state where an upper lid ofthe optical scanning device is removed;

FIG. 5 is a perspective view illustrating a state where the opticalscanning device is provided in a body frame of the image formingapparatus, as seen obliquely downward from the front surface side;

FIG. 6 is an exploded perspective view of the optical scanning deviceand the body frame which are illustrated in FIG. 5;

FIG. 7 is a sectional view taken along a VII-VII line illustrated inFIG. 3 as seen from the front surface in a direction of VII;

FIG. 8 is a perspective sectional view taken along an line illustratedin FIG. 5, as seen obliquely upward in a direction of VIII;

FIG. 9A is an enlarged perspective view of a part of a supported portionand a supporting portion which are illustrated in FIG. 8;

FIG. 9B is an enlarged perspective view of a part of a first regulatedportion and a first regulating portion which are illustrated in FIG. 8;

FIG. 9C is a vertical sectional view taken along a IXC-IXC lineillustrated in FIG. 9A;

FIG. 10 is a perspective view illustrating that a gap is providedbetween the body frame and a housing in a second rotation fulcrum unit;

FIG. 11 is a perspective view of the second rotation fulcrum unit asseen obliquely downward from the front surface side;

FIG. 12 is a top view of the second rotation fulcrum unit;

FIG. 13 is a perspective sectional view of an elastic member in theoptical scanning device, as seen obliquely upward from the front surfaceside;

FIG. 14 is a perspective view illustrating that the optical scanningdevice rotates around a virtual rotation axial line;

FIG. 15 is an enlarged plan view of a part of a second regulated portionand a second regulating portion which are illustrated in FIG. 5;

FIG. 16 is an enlarged perspective view of the part of the secondregulated portion and the second regulating portion which areillustrated in FIG. 5; and

FIG. 17 is a perspective view of the body frame of the image formingapparatus, as seen obliquely upward from the front surface side by theoptical scanning device.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments according to the disclosure will be describedwith reference to drawings. In the following description, the samecomponents will be given the same reference signs. Also, the componentswith the same reference signs have the same names and functions.Accordingly, detailed description thereof will not be repeated.

[Image Forming Apparatus]

FIG. 1 is a schematic sectional view of an image forming apparatus 100according to the embodiments of the disclosure, as seen from a frontsurface. FIG. 2 is a schematic perspective view of an image formingapparatus body 110 illustrated in FIG. 1, as seen obliquely leftdownward. FIG. 2 illustrates a state where an open/close cover 105 and amanual sheet feeding tray 82 are opened. The image forming apparatus 100according to the present embodiment is a monochrome image formingapparatus. The image forming apparatus 100 performs image formingprocessing in accordance with image data read by an image reading device1 or image data transmitted from outside. Note that, the image formingapparatus 100 may be a color image forming apparatus that forms amulticolor or monochromatic image on a sheet P.

A document feeding device 108 and the image forming apparatus body 110are included in the image forming apparatus 100. An image formingsection 102 and a sheet conveyance system 103 are included in the imageforming apparatus body 110.

The image forming section 102 includes an optical scanning device 200(specifically, an optical scanning unit), a development unit 2, aphotosensitive drum 3 that serves as an electrostatic latent imagecarrier, a cleaning unit 4, a charging device 5, and a fixing unit 7.These components are supported by a body frame 101 of the image formingapparatus 100. The image forming section 102 is covered with theopen/close cover 105 in an openable/closable manner on a front surfaceside of the image forming apparatus 100. The sheet conveyance system 103includes a sheet feeding tray 81, the manual sheet feeding tray 82, adischarge roller 31, and a discharge tray 14. An operation panel 104 isprovided on a front surface side of the image reading device 1.

The image reading device 1 which reads an image of a document G isprovided above the image forming apparatus body 110. The image readingdevice 1 includes a document placing table 107 on which the document Gis placed. The document placing table 107 is made of transparenttempered glass and has a quadrilateral shape. Additionally, the documentfeeding device 108 is provided on an upper side of the document placingtable 107. In the image forming apparatus 100, an image of the documentG read by the image reading device 1 is transmitted to the image formingapparatus body 110 as image data and the image is recorded on a sheet P.

A sheet conveyance path W1 is provided in the image forming apparatusbody 110. The sheet feeding tray 8 a or the manual sheet feeding tray 82supplies the sheet P to the sheet conveyance path W1. The sheetconveyance path W1 guides the sheet P to the discharge tray 14 via atransfer roller 10 and the fixing unit 7. The fixing unit 7 heats andfixes, onto the sheet P, a toner image formed on the sheet P. Pickuprollers 11 a and 11 b, a conveyance roller 12 a, a resist roller 13, thetransfer roller 10, a heat roller 71 and a pressure roller 72 in thefixing unit 7, and the discharge roller 31 are disposed near the sheetconveyance path W1.

In the image forming apparatus 100, the sheet P supplied from the sheetfeeding tray 81 or the manual sheet feeding tray 82 is conveyed up tothe resist roller 13. Next, the sheet P is conveyed to the transferroller 10 by the resist roller 13 at a timing at which the sheet P ismatched with a toner image on the photosensitive drum 3. The toner imageon the photosensitive drum 3 is transferred onto the sheet P by thetransfer roller 10. Then, the sheet P passes through the heat roller 71and the pressure roller 72 in the fixing unit 7 and is discharged on thedischarge tray 14 via the conveyance roller 12 a and the dischargeroller 31. In a case where image formation is performed on a rearsurface of the sheet P besides a front surface thereof, the sheet P isconveyed in a reverse direction from the discharge roller 31 to areverse sheet conveyance path W2. The sheet P is guided again to theresist roller 13 via reverse conveyance rollers 12 b to 12 b so that thesheet P is reversed. Then, the sheet P is discharged toward thedischarge tray 14 after a toner image is formed and fixed on the rearsurface, similarly to the front surface.

[Optical Scanning Device]

FIG. 3 is a perspective view of the optical scanning device 200 and anobject to be scanned, as seen obliquely downward from the front surfaceside. FIG. 4 is a perspective view illustrating a state where an upperlid 202 of the optical scanning device 200 is removed. Note that, in thefigures, a reference sign X represents a main scanning direction (depthdirection in this example), and reference signs X1 and X2 respectivelyrepresent one side (back surface side) and the other side (front surfaceside). A reference sign Y represents a sub scanning direction(up-and-down direction or vertical direction in this example) orthogonalto the main scanning direction X. A reference sign Z represents anorthogonal direction (right-and-left direction as seen from the frontsurface in this example) orthogonal to both of the main scanningdirection X and the sub scanning direction Y, and reference signs Z1 andZ2 respectively represent one side (right side as seen from the frontsurface) and the other side (left side as seen from the front surface).

The optical scanning device 200 includes a light source unit 210, anincident optical system 220, a deflector 230 (polygon mirror), anoutgoing optical system 240, and a detection unit. The light source unit210 includes a light source 211. The light source 211 outputs a beam BM.The incident optical system 220 is disposed between the light sourceunit 210 and the deflector 230 on an optical path of the beam BM. Theincident optical system 220 causes the beam BM output from the lightsource unit 210 to be incident on the deflector 230. The deflector 230performs deflection scanning in the main scanning direction X with thebeam BM made incident from the light source unit 210 via the incidentoptical system 220. The outgoing optical system 240 is disposed betweenthe deflector 230 and a surface to be scanned F (surface of thephotosensitive drum 3 in this example) of an object to be scanned on theoptical path of the beam BM. The outgoing optical system 240 irradiatesthe surface to be scanned F with the beam BM output from the deflector230. The detection unit 250 detects the beam BM output from thedeflector 230. The light source unit 210, the incident optical system220, the deflector 230, the outgoing optical system 240, and thedetection unit 250 are accommodated in a housing 201.

In the optical scanning device 200, the beam DM output from the lightsource unit 210 is caused to be incident on the deflector 230 via theincident optical system 220, the deflector 230 performs deflectionscanning in the main scanning direction X with the beam BM, and imageinformation is written on the surface to be scanned F, which is thesurface of the photosensitive drum 3, via the outgoing optical system240 while the detection unit 250 performs detection. Note that, thesurface to be scanned F is regularly scanned with the beam BM in themain scanning direction X, but the photosensitive drum 3 rotates in arotation direction 5 (refer to FIG. 3), so that the scanning is able tobe performed on the photosensitive drum 3 also in the sub scanningdirection Y.

First Embodiment

FIG. 5 is a perspective view illustrating a state where the opticalscanning device 200 is provided in the body frame 101 of the imageforming apparatus 100, as seen obliquely downward from the front surfaceside. FIG. 6 is an exploded perspective view of the optical scanningdevice 200 and the body frame 101 which are illustrated in FIG. 5 FIG. 7is a sectional view taken along a VII-VII line illustrated in FIG. 5, asseen from the front surface in a direction of VII. FIG. 8 is aperspective sectional stew taken along an VIII-VIII line illustrated inFIG. 5, as seen obliquely upward in a direction of VIII.

FIG. 9A is an enlarged perspective view of a part IXA of a supportedportion 201 a and a supporting portion 101 a which are illustrated inFIG. 8. FIG. 95 is an enlarged perspective view of a part IXB of a firstregulated portion 201 c and a first regulating portion 101 e illustratedin FIG. 8. FIG. 9C is a vertical sectional view taken along a IXC-IXCline illustrated in FIG. 9A.

FIG. 10 is a perspective view illustrating that a gap d is providedbetween the body frame 101 and the housing 201 in a second rotationfulcrum unit 320. FIG. 11 is a perspective view of toe second rotationfulcrum unit 320 as seen obliquely downward from the front surface side.FIG. 12 is a top view of the second rotation fulcrum unit 320. FIG. 13is a perspective sectional view of an elastic member 330 in the opticalscanning device 200, as seen obliquely upward from the front surfaceside. FIG. 14 is a perspective view illustrating that the opticalscanning device 200 rotates around a virtual rotation axial line β.

The image forming apparatus 100 includes a first rotation fulcrum unit310 and the second rotation fulcrum unit 320. The first rotation fulcrumunit 310 and the second rotation fulcrum unit 320 are provided outsideon any one of sides (one side X1 in the example) in the main scanningdirection X and respectively provided on the one side Z1 and on theother side Z2 in the orthogonal direction Z of the optical scanningdevice 200. The first rotation fulcrum unit 310 is provided outside ascanning area α of the beam BM in the main scanning direction X. Theoptical scanning device 200 is provided rotatably around the virtualrotation axial line β. The scanning area α is an area for irradiatingthe surface to be scanned F of the object to be scanned with the beamBM. The virtual rotation axial line β is a straight line connecting thefirst rotation fulcrum unit 310 and the second rotation fulcrum unit320.

According to the present embodiment, the first rotation fulcrum unit 310and the second rotation fulcrum unit 320 are provided outside on any oneof the sides in the main scanning direction X and respectively providedon the one side Z1 and on the other side Z2 in the orthogonal directionZ of the optical scanning device 200. Accordingly, the virtual rotationaxial line β is enabled to pass through an outside of the scanning areaα of the optical scanning device 200 in the main scanning direction X.Thereby, a beam scanning trajectory γ (refer to FIG. 14) that is ascanning trajectory of the beam BM output from the optical scanningdevice 200 is inclined to one side with respect to the main scanningdirection X with a point Q in the outside of the scanning area α as acenter. Thus, the beam scanning trajectory γ is only desired to beadjusted so as to be along the main scanning direction X while the otherend side of the scanning area α in the main scanning direction is beingconfirmed. Accordingly, it is possible to realize simplification of anadjustment operation for adjusting the beam scanning trajectory γ so asto be along the main scanning direction X.

In the present embodiment, in the housing 201 of the optical scanningdevice 200, the supported portion 201 a is provided on the one side X1in the main scanning direction X and also on the one side Z1 in theorthogonal direction Z. The supporting portion 101 a is provided in thebody frame 101 of the image forming apparatus 100. The supportingportion 101 a supports the supported portion 201 a rotatably around thevirtual rotation axial line β. The first rotation fulcrum unit 310 iscomposed of a contact part between the supported portion 201 a and thesupporting portion 101 a. Accordingly, the supported portion 201 a inthe housing 201 of the optical scanning device 200 is reliably supportedby the supporting portion 101 a in the body frame 101 of the imageforming apparatus 100. Thereby, the beam scanning trajectory γ is ableto be reliably adjusted so as to be along the main scanning direction X.

Specifically, the supported portion 201 a protrudes toward the one sideZ1 from an end of the housing 201 on the one side Z1 in the orthogonaldirection Z. The supporting portion 101 a is configured to have arecessed shape recessed to the one side Z1 in the orthogonal direction Zso that the supported portion 201 a is able to be inserted. A dimensionD1 (refer to FIG. 9A) of the supporting portion 101 a in the subscanning direction Y is set to be longer than a dimension of thesupported portion 201 a in the sub scanning direction Y by apredetermined distance (predetermined distance of such a degree that thesupported portion 201 a is able to be smoothly inserted into thesupporting portion 101 a). Both ends of the supported portion 201 a inthe sub scanning direction Y have curved parts 201 a 1 and 201 a 1(refer to FIG. 9C) that are curved in a concave shape along the mainscanning direction X. Thereby, the optical scanning device 200 is ableto smoothly rotate around the virtual rotation axial line β.

In the present embodiment, a placement unit 101 b on which the opticalscanning device 200 is placed is provided in the body frame 101 of theimage forming apparatus 100. A protrusion 101 c that protrudes toward aside of the optical scanning device 200 is provided in the placementunit 101 b. The second rotation fulcrum unit 320 is composed of acontact part between the protrusion 101 c and a contacting portion 201 bin which the protrusion 101 c contacts the housing of the opticalscanning device 200. Accordingly, the contacting portion 201 b in thehousing 201 of the optical scanning device 200 is able to be reliablycontacted with the protrusion 101 c in the body frame 101 of the imageforming apparatus 100. Thereby, the beam scanning trajectory γ is ableto be stably adjusted so as to be along the main scanning direction X.

Specifically, the gap d (refer to FIG. 10) is provided between the bodyframe 101 and the housing 201 in the second rotation fulcrum unit 320.Thereby, a rotation range around the virtual rotation axial line β ofthe optical scanning device 200 is able to be enlarged.

In the present embodiment, the protrusion 101 c comes into point contactwith the contacting portion 201 b. Accordingly, the contacting portion201 b in the housing 201 of the optical scanning device 200 is able tobe contacted with the protrusion 101 c in the body frame 101 of theimage forming apparatus 100 with little friction resistance. Thereby,the beam scanning trajectory γ is able to be smoothly adjusted so as tobe along the main scanning direction X.

Specifically, the protrusion 101 c is formed into a stick shape(cylindrical shape in this example). A tip of the protrusion 101 c isformed into a hemispherical shape. Thereby, the tip of the protrusion101 c is able to come into point contact with the contacting portion.201 b. Note that, the tip of the protrusion 101 c may be in an ovalspherical shape, a pyramid shape, or a conical shape. The protrusion 101c may be in an elliptic cylindrical shape or a prismatic shape.

In the present embodiment, the image forming apparatus 100 furtherincludes the elastic member 330. The elastic member 330 presses thecontacting portion 201 b toward the protrusion 101 c. Accordingly, theelastic member 330 allows the contacting portion 201 b in the housing201 of the optical scanning device 200 to be reliably held by theprotrusion 101 c in the body frame 101 of the image forming apparatus100. Thereby, the beam scanning trajectory γ is able to be furtherstably adjusted so as to be along the main scanning direction X.

Specifically, the elastic member 330 is a leaf spring. A through hole331 that penetrates along a thickness direction is provided in theelastic member 330. In the body frame 101, a fixed portion 11 d (femalehole) is provided so that a center thereof passes through the virtualrotation axial line β. The elastic member 330 is fixed (screwed) to thefixed portion 101 d when a fixing member S1 (screw) (refer to FIG. 6)passes through the through hole 331 in a state where the housing 201 ispressed toward the protrusion 101 c. Thereby, the contacting portion 201b is able to be reliably pressed toward the protrusion 101 c. Aprojection 332 that protrudes toward a side of the housing 201 isprovided in a pressing portion of the elastic member 330 which pressesthe housing 201. This makes it possible to concentrically press thecontacting portion 201 b toward the protrusion 101 c. In this example,the projection 332 is configured to protrude toward the side of thehousing 201 by recessing a metal member having a plate shape toward theside of the housing 201.

Second Embodiment

In the present embodiment, in the housing 201 of the optical scanningdevice 200, the first regulated portion 201 c is provided on the otherside X2 in the main scanning direction X and also on toe one side Z1 inthe orthogonal direction Z. The first regulating portion 101 e isprovided in the body frame 101 of the image forming apparatus 100. Thefirst regulating portion 101 e regulates rotation of the opticalscanning device 200 around the virtual rotation axial line β bycontacting the first regulated portion 201 c. This makes it possible toregulate excessive rotation of the optical scanning device 200 aroundthe virtual rotation axial line β by contact of the first regulatedportion 201 c and the first regulating portion 101 e. Thereby, it ispossible to realize simplification of the adjustment operation foradjusting the beam scanning trajectory γ.

Specifically, the first regulated portion 201 c protrudes toward the oneside Z1 from an end portion of the housing 201 on the one side Z1 in theorthogonal direction Z. The first regulating portion 101 e is configuredto have a recessed shape recessed to the one side Z1 in the orthogonaldirection Z so that the first regulated portion 201 c is able to beinserted. A dimension D2 (refer to FIG. 9B) of the first regulatingportion 101 e in the sub scanning direction Y is set to be longer than adimension of the first regulated portion 201 c in the sub scanningdirection Y by a predetermined distance (distance of such a degree thatthe optical scanning device 200 is able to smoothly rotate around thevirtual rotation axial line β).

Third Embodiment

FIGS. 15 and 16 are an enlarged plan view and an enlarged perspectiveview of a part C3 of a second regulated portion 201 d and a secondregulating portion 101 f which are illustrated in FIG. 5, respectively.Here, the second regulated portion 201 d and the second regulatingportion 101 f will be described below with reference to FIG. 10 throughFIG. 12 in addition to FIGS. 15 and 16.

In the present embodiment, second regulated portions 201 d and 201 d(refer to FIG. 10 through FIG. 12 and FIGS. 15 and 16) are provided inthe housing 201 of the optical scanning device 200. In the body frame101 of the image forming apparatus 100, second regulating portions 101 fand 101 f (refer to FIG. 10 through FIG. 12 and FIGS. 15 and 16) areprovided. The second regulating portions 101 f and 101 f permit rotationof the optical scanning device 200 around the virtual rotation axialline β while regulating movement of the optical scanning device 200 inthe orthogonal direction Z by contacting the second regulated portions201 d and 201 d. This makes it possible to regulate excessive movementof the optical scanning device 200 in the orthogonal direction Z bycontact of the second regulated portions 201 d and 201 d and the secondregulating portions 101 f and 1011, in a state where the rotation of theoptical scanning device 200 around the virtual rotation axial line β ispermitted. Thereby, it is possible to realize simplification of theadjustment operation for adjusting the beam scanning trajectory γ.

Specifically, one second regulated portion 201 d and one secondregulating portion 101 f are provided in the housing 201 on the one sideX1 in the main scanning direction X and also on the other side Z2 in theorthogonal direction Z. The other second regulated portion 201 d and theother second regulating portion 101 f are provided in the housing 201 onthe other side X2 in the main scanning direction X and also on the otherside Z2 in the orthogonal direction Z. The second regulated portions 201d and 201 d are through holes (refer to FIG. 10 through FIG. 12) thatpenetrate along the sub scanning direction Y or through grooves (referto FIGS. 15 and 16). Each of the second regulated portions 201 d and 201d is formed into a quadrilateral shape. Each of the second regulatingportions 101 f and 101, is a protrusion that protrudes toward the sideof the optical scanning device 200 from the body frame 101. Each of thesecond regulating portions 101 f and 101 f is formed into a stick shape(cylindrical shape in this example). A dimension D3 (refer to FIGS. 12and 15) of each of the second regulated portions 201 d and 201 d in theorthogonal direction Z is set to be longer than a dimension of each ofthe second regulating portions 101 f and 101 f in the orthogonaldirection Z by a predetermined distance (predetermined distance of sucha degree that the second regulating portions 101 f and 101 f are able tobe smoothly inserted into the second regulated portions 201 d and 201 d,respectively). A dimension D4 (refer to FIGS. 12 and 15) of each of thesecond regulated portions 201 d and 201 d in the main scanning directionX is set to be longer than a dimension of each of the second regulatingportions 101 f and 101 f in the main scanning direction X by apredetermined distance (distance of such a degree that the opticalscanning device 200 is able to smoothly rotate around the virtualrotation axial line β). Each of the second regulating portions 101 f and101 f may be in an elliptic cylindrical shape or a prismatic shape. Eachof the second regulated portions 201 d and 201 d may be in a round shapeor an elliptic shape.

Fourth Embodiment

In the main scanning direction X, the optical scanning device 200 may beheld on a side (one side X1 in the example) of the first rotationfulcrum unit 310 and the second rotation fulcrum unit 320. However, inthis case, positional accuracy of the optical scanning device 200 afteradjustment of the beam scanning trajectory γ is easily lowered.

FIG. 17 is a perspective view of the body frame 101 of the image formingapparatus 100, as seen obliquely upward from the front surface side bythe optical scanning device 200. In the present embodiment, a holdingportion. 340 which holds the optical scanning device 200 on a side (theother side X2 in this example) opposite to the first rotation fulcrumunit 310 and the second rotation fulcrum unit 320 in the main scanningdirection X is included. This makes it possible for the holding portion340 to hold the optical scanning device 200 on a side opposite to thevirtual rotation axial line β in the main scanning direction X. Aposition of the optical scanning device 200 after adjustment of the beamscanning trajectory is thereby able to be accurately maintained.

Specifically, penetrating portions (through holes or through grooves)101 g and 101 g that penetrate along the main scanning direction X areprovided on a front surface side of the body frame 101. Fixed portions(female holes) 201 e and 201 e are provided on a front surface side ofthe housing 201. The holding portion 340 is constituted by acorresponding one of the penetrating portions 101 g and 101 g and acorresponding one of the fixed portions 201 e and 201 e. In the opticalscanning device 200, fixing members (screws) S2 and S2 respectively passthrough the penetrating portions 101 g and 101 g and are respectivelyfixed (screwed) to the fixed portions 201 e and 201 e in a state wherethe beam scanning trajectory γ is adjusted. This makes it possible tohold the optical scanning device 200 on the side opposite to the virtualrotation axial line β in the main scanning direction X.

Usually, it is difficult to ensure an operation space where theadjustment operation for adjusting the beam scanning trajectory γ isperformed, except for a place on the front surface side (a side of theoperation panel 104, a side of the open/close cover 105, a drawing-outside of the sheet feeding tray 81) of the image forming apparatus 100.Accordingly, it is difficult to perform the adjustment operation foradjusting the beam scanning trajectory γ.

In this respect, in the present embodiment, the optical scanning device200 is configured so that a position of the optical scanning device 200is adjustable from the front surface side of the image forming apparatus100. Accordingly, an operator is enabled to adjust the position of theoptical scanning device 200 from the front surface side of the imageforming apparatus 100. Thereby, it is possible to realize simplificationof the adjustment operation for adjusting the beam scanning trajectoryγ.

Specifically, the operator loosens the fixing members (screws) S2 and S2from the front surface side by using a jig to thereby adjust the beamscanning trajectory γ while moving the optical scanning device 200 up ordown with the fixing members S2 and S2. Then, the operator temporarilyfixes the optical scanning device 200 with the fixing members S2 and S2.Such an operation is repeated until the beam scanning trajectory γ isaligned with the main scanning direction X. The operator securely fixesthe optical scanning device 200 with the fixing members S2 and S2 afterthe beam scanning trajectory γ is aligned with the main scanningdirection X.

Another Embodiment

In the present embodiment, the virtual rotation axial line β is providedon the one side X1 in the main scanning direction X, but may be providedon the other side X2.

The disclosure is not limited to any of the embodiments described aboveand is able to be implemented in other various forms. Any of theembodiments is merely an example in all respects and should not beconstrued as limitative. The scope of the disclosure is indicated by thescope of the claims and is not restricted in any way by the text of thespecification. Moreover, all variations and modifications falling withina scope equivalent to the scope of the claims are included in the scopeof the disclosure.

The present disclosure contains subject matter related to that disclosedin Japanese Priority Patent Application JP 2018-000649 filed in theJapan Patent Office on Jan. 5, 2018, the entire contents of which arehereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. An image forming apparatus including an opticalscanning device that scans an object to be scanned with a beam in a mainscanning direction, the image forming apparatus comprising a firstrotation fulcrum unit and a second rotation fulcrum unit that arerespectively provided in the optical scanning device on one side and onthe other side in an orthogonal direction orthogonal to the mainscanning direction, wherein the first rotation fulcrum unit is providedoutside a scanning area of the beam in the main scanning direction, andthe optical scanning device is provided rotatably around a virtualrotation axial line connecting the first rotation fulcrum unit and thesecond rotation fulcrum unit.
 2. The image forming apparatus accordingto claim 1, wherein a supported portion is provided on the one side in ahousing of the optical scanning device, a supporting portion thatsupports the supported portion rotatably around the virtual rotationaxial line is provided in a body frame of the image forming apparatus,and the first rotation fulcrum unit is composed of the supported portionand the supporting portion.
 3. The image forming apparatus according toclaim 1, wherein a placement unit on which the optical scanning deviceis placed is provided in a body frame of the image forming apparatus, aprotrusion that protrudes toward a side of the optical scanning deviceis provided in the placement unit, and the second rotation fulcrum unitis composed of the protrusion and a contacting portion at which theprotrusion contacts a housing of the optical scanning device.
 4. Theimage forming apparatus according to claim wherein the protrusion comesinto point contact with the contacting portion.
 5. The image formingapparatus according to claim 3, further comprising an elastic memberthat presses the contacting portion toward the protrusion.
 6. The imageforming apparatus according to claim 1, wherein a first regulatedportion is provided on the other side in the main scanning direction ina housing of the optical scanning device, and a first regulating portionthat regulates rotation of the optical scanning device around thevirtual rotation axial line by contacting the first regulated portion isprovided in a body frame of the image forming apparatus.
 7. The imageforming apparatus according to claim 1, wherein a second regulatedportion is provided in a housing of the optical scanning device, and asecond regulating portion that permits rotation of the optical scanningdevice around the virtual rotation axial line while regulating movementof the optical scanning device in the orthogonal direction by contactingthe second regulated portion is provided in a body frame of the imageforming apparatus.
 8. The image forming apparatus according to claim 1,further comprising a holding portion that holds the optical scanningdevice on a side opposite to the first rotation fulcrum unit and thesecond rotation fulcrum unit in the main scanning direction.
 9. Theimage forming apparatus according to claim 1, wherein the opticalscanning device is configured so that a position of the optical scanningdevice is adjustable from front surface side of the image formingapparatus.